Studies have shown that for the typical search service user, at least half of the queries that a user issues are attempts to re-find information that the user has seen in a previous search session or previously in the same search session. Users are often unsuccessful in re-finding the information due to various factors, which include the inability of the user to remember the exact search terms previously used, rank changes within the index, and the inability for the user to recognize search results that they have previously seen.